Automotive headlamps, which are given the standard designation H1 lamps, H3 lamps or H4 lamps, operate at extremely high temperatures. The filament of the lamp must be accurately positioned with respect to an engagement or holder ring which fits against a portion of the headlamp reflector so that a predetermined light distribution will result when the lamp-reflector combination is installed in an automotive vehicle. The bulbs of such lamps, thus, frequently are connected to a base without the use of a connecting cement. Typically, the lamps are single-ended glass bulbs which terminate in a pinch or press seal at one end, which may be defined as the press seal end, and a top end, usually having an exhaust tip through which the interior of the lamp bulb had been exhausted, and then a fill gas introduced into the bulb. Current supply leads extend outwardly of the press seal, and at least one incandescent filament is located interiorly of the bulb, electrically connected to the current supply leads. It has previously been proposed to use two-part base constructions, having an outer sleeve and a base plug element of insulating material. A holder element surrounds the pinch or press seal of the bulb and is coupled to the base sleeve to position the bulb with respect to the base sleeve which, also, may be used as a reference element to determine the position of the filament with respect to the reflector, and which may have a holding or adjustment ring formed thereon. The connecting terminals for the lamp extend, typically, through the base and are electrically connected to the current supply leads.
Lamps of this type, with a combination metal-insulating material, for example plastic material bases, are used frequently in connection with automotive headlights and one type of lamp is described in the referenced U.S. Pat. No. 4,412,273, Helbig, the disclosure of which is hereby incorporated by reference, assigned to the assignee of the present application. The Helbig U.S. Pat. No. 4,412,273 describes a lamp for use with a reflector which, however, uses a comparatively complex base. The base sleeve is retained in a receiving portion of a disk element. The optical quality of the headlamp depends on the quality of this attachment which should have as little play as possible.
U.S. Pat. No. 4,641,056, Sanders et al, proposes the construction of a base of synthetic material which is formed of two parts, connected by ultrasonic bonding or welding. One of the parts is a hollow cylinder, the second one forming the base or bottom wall thereof. The hollow cylindrical part surrounds a cylindrical base sleeve and is mechanically connected therewith by interengaging notches and projections. The terminal tabs or terminal spades are connected to the base wall portion by ultrasonic welding. U.S. Pat. No. 4,751,421, Braun, describes a holder element for the bulb. In this construction, a metal holder is coupled to a plastic base element.